河套地区一次强沙尘暴天气过程分析

文章利用Micaps系统、地面常规观测气象资料,通过对高空、地面、风场、物理量场及卫星云图特征分析表明:前期的干暖气候及上游充足的沙源是形成巴彦淖尔市沙尘暴不可缺少的环境因素和物质基础;500~700hPa贝加尔湖低涡底部的西北气流风力在16~30m·s-1,并形成一支急流带,冷平流在10个纬度内有5根等温线的密集带,等高线与等温线交角≥45℃,是形成沙暴天气的前提条件之一;影响河套地区的地面冷锋,其后部的地面冷高压紧随其后,高低压之间气压梯度及地面风的加大以及沙尘暴出现前期近地面气温增温明显,大气层结不稳定度显著增大,为沙尘暴天气的爆发提供了动力条件和热力条件;通过对物理量场的分析,整层的干暖条件、强烈的上升运动及低层辐合高层辐散形成的次级环流的垂直作用,是沙尘暴发生发展的动力源泉;高空涡旋云系的发展配合地面辐合上升气流,表明了高低空强烈的抽吸作用对沙尘暴爆发的贡献。

Analysis on a Weather Process of Severe Sand and Dust Storm in Hetao Area

According to MICAPS system and meteorological data provided by ground routine observation, the data of the high altitude, the ground, the wind field, the physical quantity field and the satellite cloud picture were analyzed. The results showed that： the previous dry and warm climate and the upstream plenty of sand source were the indispensable environmental factors and material basis for forming sand-dust storm in Bayan Nur City. In 500-700 hPa, the velocity of the northwest airflow at the bottom of the Lake Baikal vortex is among 16 to 30 m/s, and becoming a jet stream. Cold advection has a dense band with 5 isotherms in 10 latitude. The angle of the contours and the isotherm is equal or greater than 45 degrees. All above are prerequisites for the formation of sand-dust storms. The cold front affecting the Hetao area, the cold high pressure that followed cold front, the pressure gradient between high and low pressure and the surface wind increasing, the near-surface air temperature increased significantly at the prophase of sand-dust storm appearance, and the instability degree of atmospheric stratification increased significantly, which provided the dynamic conditions and thermal conditions for the outbreak and uptrend of sand-dust storms. Through the analysis of physical field, the power source of sand-dust storms development is including the whole layer of dry and warm conditions, strong upward movement as well as the formation of the vertical role of secondary circulation by low-level convergence and upper-level divergence. The development of high-altitude vortex cloud system coordinates the ground convergence updraft, which indicates that the strong suction of the high and low altitude contribute a lot to the outbreak of sand-dust storms.